Intrapartum maternal oxygen may not be beneficial for resuscitating fetuses with category II heart tracings

Key clinical point: Room air was not inferior to maternal oxygen for the resuscitation of a fetus who developed category II heart rhythms.

Major finding: Umbilical artery lactate was 3.4 mmol/L in the oxygen group and 3.5 mmol/L in the room air group.

Study details: The trial randomized 114 women.

Disclosures: The study was sponsored by the Washington University School of Medicine. Dr. Raghuraman had no financial disclosures.

Source: Raghuraman N et al. Am J Obstet Gynecol. 2018 Jan;218:S7.

REPORTING FROM THE PREGNANCY MEETING

DALLAS – Room air was not inferior to maternal oxygen supplementation for the management of category II fetal heart tracings in a clinical trial.

Umbilical cord blood lactate – a marker of fetal acidosis caused by oxygen deprivation – was virtually identical whether the women received oxygen or remained on room air, Nandini Raghuraman, MD, said at the meeting sponsored by the Society for Maternal-Fetal Medicine. Other blood gas measures were similar as well, and there were no differences in the number of cesarean sections or operative vaginal deliveries, said Dr. Raghuraman of Washington University, St. Louis.

Michele G Sullivan

Dr. Nandini Raghuraman

The study is the first step in challenging the widely accepted practice of automatic maternal oxygen as a way of resuscitating fetuses who develop nonreassuring fetal heart rhythms during labor, she said.

“Our results suggest that room air is an acceptable alternative. However, we do need further studies, including a superiority trial.”

She noted that three randomized studies have compared oxygen to room air. “None demonstrated benefit to the fetus, and some demonstrated harm, including higher rates of delivery room resuscitation and higher neonatal acidemia. Importantly, all of these studies excluded patients with abnormal fetal heart tracings, which is the primary indication for maternal oxygen during labor and delivery.”

Her study comprised 114 women in active labor with a normal singleton fetus that developed category II heart tracings. Women received either oxygen at 10 L per minute by face mask, or stayed on room air with no face mask. The intervention continued to delivery.

The women were a mean age of 27.5 years; about three-quarters were black. Most (70%) had a labor induction, and 89% had received oxytocin. There were no between-group differences in the need for other fetal resuscitation strategies, including IV fluid bolus, total IV fluids, discontinuation or decrease in oxytocin, maternal repositioning, amnioinfusion, and time from randomization to delivery.

There was no difference in the primary outcome: Lactate levels were 3.4 mmol/L in the oxygen group and 3.5 mmol/L in the room air group.

Dr. Raghuraman also looked at lactate levels among those neonates who had recurrent decelerations and who did not. There was no significant difference in this comparison.

The secondary outcome of umbilical artery blood gases included measures of pH, base excess, partial CO2, and partial oxygen. There were no significant differences in any of these comparisons. Partial O2 was higher (though not significantly so) in the samples that had been exposed to oxygen, as would be expected, Dr. Raghuraman noted.

There were fewer cesarean deliveries among the room air group (4% vs. 12.5%), although this was not statistically significant. Two neonates in the oxygen group were delivered by C-section for nonreassuring fetal heart tracings. There were more operative vaginal deliveries in the room air group (11.8% vs. 2%), but this difference was not statistically significant, with a wide confidence interval (0.71-45.2).

“These results alone are not enough to be practice changing,” Dr. Raghuraman said. “Before we can do that, we need to address efficacy, which this study has called into question. But we also need to explore the results of safety and harm, and until we do so our nurses will likely continue their usual practice of putting these patients on supplement oxygen.”